Security breaches again made big news in 2014. Yet despite years of headline stories about security leaks and distributed denial-of-service (DDoS) attacks and repeated admonishments from security professionals that businesses (and individuals) needed to do a better job protecting sensitive data, many businesses are still unprepared or not properly protected from a variety of security threats.

Indeed, according to Trustwave’s recent 2014 State of Risk Report, which surveyed 476 IT professionals about security weaknesses, a majority of businesses had no or only a partial system in place for controlling and tracking sensitive data.

So, what can companies do to better protect themselves and their customers’, sensitive data from security threats? CIO.com queried dozens of security and IT experts to find out. Following are the six most likely sources, or causes, of security breaches and what businesses can, and should, do to protect against them.

Risk No. 1: Disgruntled Employees

“Internal attacks are one of the biggest threats facing your data and systems,” states Cortney Thompson, CTO of Green House Data. “Rogue employees, especially members of the IT team with knowledge of and access to networks, data centers and admin accounts, can cause serious damage,” he says. Indeed, “there [were] rumors that the Sony hack was not [carried out by] North Korea but [was actually] an inside job.

Solution: “The first step in mitigating the risk of privileged account exploitation is to identify all privileged accounts and credentials [and] immediately terminate those that are no longer in use or are connected to employees that are no longer at the company,” says Adam Bosnian, executive vice president, CyberArk.

“Next, closely monitor, control and manage privileged credentials to prevent exploitation. Finally, companies should implement necessary protocols and infrastructure to track, log and record privileged account activity [and create alerts, to] allow for a quick response to malicious activity and mitigate potential damage early in the attack cycle.”

Risk No. 2: Careless or Uninformed Employees

“A careless worker who forgets [his] unlocked iPhone in a taxi is as dangerous as a disgruntled user who maliciously leaks information to a competitor,” says Ray Potter, CEO, SafeLogic. Similarly, employees who are not trained in security best practices and have weak passwords, visit unauthorized websites and/or click on links in suspicious emails or open email attachments pose an enormous security threat to their employers’ systems and data.

Solution: “Train employees on cyber security best practices and offer ongoing support,” says Bill Carey, vice presdient of Marketing for RoboForm. “Some employees may not know how to protect themselves online, which can put your business data at risk,” he explains. So it’s essential to “hold training sessions to help employees learn how to manage passwords and avoid hacking through criminal activity like phishing and keylogger scams. Then provide ongoing support to make sure employees have the resources they need.”

Also, “make sure employees use strong passwords on all devices,” he adds. “Passwords are the first line of defense, so make sure employees use passwords that have upper and lowercase letters, numbers and symbols,” Carey explains.

“It’s also important to use a separate password for each registered site and to change it every 30 to 60 days,” he continues. “A password management system can help by automating this process and eliminating the need for staff to remember multiple passwords.”

Encryption is also essential.

“As long as you have deployed validated encryption as part of your security strategy, there is hope,” says Potter. “Even if the employee hasn’t taken personal precautions to lock their phone, your IT department can execute a selective wipe by revoking the decryption keys specifically used for the company data.”

To be extra safe, “implement multifactor authentication such as One Time Password (OTP), RFID, smart card, fingerprint reader or retina scanning [to help ensure] that users are in fact who you believe they are,” adds Rod Simmons, product group manager, BeyondTrust. “This helps mitigate the risk of a breach should a password be compromised.”

Risk No. 3: Mobile Devices (BYOD)

“Data theft is at high vulnerability when employees are using mobile devices [particularly their own] to share data, access company information, or neglect to change mobile passwords,” explains Jason Cook,CTO & vice president of Security, BT Americas. “According to a BT study, mobile security breaches have affected more than two-thirds (68 percent) of global organizations in the last 12 months.”

Indeed, “as more enterprises embrace BYOD, they face risk exposure from those devices on the corporate network (behind the firewall, including via the VPN) in the event an app installs malware or other Trojan software that can access the device's network connection,” says Ari Weil, vice president, Product Marketing, Yottaa.

Solution: Make sure you have a carefully spelled out BYOD policy. “With a BYOD policy in place, employees are better educated on device expectations and companies can better monitor email and documents that are being downloaded to company or employee-owned devices,” says Piero DePaoli, senior director, Global Product Marketing, Symantec. “Monitoring effectively will provide companies with visibility into their mobile data loss risk, and will enable them to quickly pinpoint exposures if mobile devices are lost or stolen.”

Similarly, companies should “implement mobile security solutions that protect both corporate data and access to corporate systems while also respecting user’s privacy through containerization,” advises Nicko van Someren, CTO, Good Technology. “By securely separating business applications and business data on users’ devices, containerization ensures corporate content, credentials and configurations stay encrypted and under IT’s control, adding a strong layer of defense to once vulnerable a points of entry.”

You can also “mitigate BYOD risks with a hybrid cloud,” adds Matthew Dornquast, CEO and cofounder, Code42. “As unsanctioned consumer apps and devices continue to creep into the workplace, IT should look to hybrid and private clouds for mitigating potential risks brought on by this workplace trend,” he says. “Both options generally offer the capacity and elasticity of the public cloud to manage the plethora of devices and data, but with added security and privacy—such as the ability to keep encryption keys on-site no matter where the data is stored—for managing apps and devices across the enterprise.”